Wireless power transfer is implemented with the combination of an energy transmitter which transfers power and an energy receiver which receives power. They are connected electromagnetically by inductive coupling, capacitive coupling or other coupling approaches. Communication normally occurs between the transmitter and the receiver for tasks such as device identification, power transfer contract negotiation and power transfer control. An economic way to implement such communication is to directly modulate the power that is being transferred, without adding extra communication channels. However, such power modulation can often introduce undesirable and unpredictable variations in power output which are not favored by many loads.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.